The antimicrobial quinolone compounds, (3S,5S)-7-[3-amino-5-methyl-piperidinyl]-1-cyclopropyl-1,4-dihydro-8-methoxy-4-oxo-3-quinolinecarboxylic acid, and (3S,5R)-7-[3-amino-5-methyl-piperidinyl]-1-cyclopropyl-1,4-dihydro-8-methoxy-4-oxo-3-quinolinecarboxylic acid are disclosed in the U.S. Pat. No. 6,329,391, which is herein incorporated by reference in its entirety. Synthesis of various quinolone compounds have been reported in the literature, e.g., U.S. Pat. No. 6,329,391; U.S. Pat. No. 6,803,469; B. Ledoussal et al., “Non 6-Fluoro Substituted Quinolone Antibacterials: Structure and Activity”, J. Med. Chem., Vol. 35, p. 198-200 (1992); V. Cecchetti et al., “Studies on 6-Aminoquinolines: Synthesis and Antibacterial Evaluation of 6-Amino-8-methylquinolones”, J. Med. Chem., Vol. 39, pp. 436-445 (1996); V. Cecchetti et al., “Potent 6-Desfluoro-8-methylquinolones as New Lead Compounds in Antibacterial Chemotherapy”, J. Med. Chem., Vol. 39, pp. 4952-4957 (1996)).
The above-mentioned compounds are useful to treat microbial infections. However, what salt forms would yield a suitable preparation for the manufacture of a pharmaceutically acceptable composition is not known. Therefore, there is a need in the art to develop useful salt forms and polymorphs of these antimicrobial compounds.